A Study of the Time Dependence in Fracture Processes Relating to Service Prediction of Adhesive Joints and Advanced Composites.
Abstract
Problems related to fracture of bonded structures and composites were studied with emphasis on the time dependence of the failure process. Three subject areas in this theses are identified: (a) Residual stresses due to changes in temperature through the glass transition range. It is found that determination of the creep compliance or of the relaxation modulus is the most important material property for accurate stress determination general experimental and analytical agreement prevails. (b) In temperature 'accelerated' crack propagation tests along interfaces it is found that crack propagation stops upon raising the temperature. The reason for this 'unexpected' behavior is that with raising the temperature the elimination of residual stresses overcomes the reduction of viscosity so that crack arrest becomes possible. (c) Fatigue crack propagation is studied for a viscoelastic material. In contrast to metals the rate of crack growth per cycle is strongly affected by the frequency, declining with increasing frequency. However, the average velocity (cm/sec) per cycle increases with frequency. Thus it is more important to consider the time under stress than merely the number of cycles.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 30, 1984
- Accession Number
- ADA152064
Entities
People
- W. G. Knauss
Organizations
- California Institute of Technology